Electrochemical Fabrication Method and Apparatus for Producing Three-Dimensional Structures Having Improved Surface Finish

ABSTRACT

An electrochemical fabrication process produces three-dimensional structures (e.g. components or devices) from a plurality of layers of deposited materials wherein the formation of at least some portions of some layers are produced by operations that remove material or condition selected surfaces of a deposited material. In some embodiments, removal or conditioning operations are varied between layers or between different portions of a layer such that different surface qualities are obtained. In other embodiments varying surface quality may be obtained without varying removal or conditioning operations but instead by relying on differential interaction between removal or conditioning operations and different materials encountered by these operations.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/387,958 (Microfabrica Docket No. P-US050-A-MG), filed Mar. 13, 2003which in turn claims the benefit of U.S. Provisional Patent ApplicationNo. 60/364,261 filed Mar. 13, 2002 and U.S. Provisional Application No.60/379,130, filed May 7, 2002. All of these applications are herebyincorporated herein by reference as if set forth in full herein.

FIELD OF THE INVENTION

The present invention relates generally to the formation ofthree-dimensional structures (e.g. components or devices) usingelectrochemical fabrication methods via a layer-by-layer build up ofdeposited materials where at least some layers are subjected to surfaceconditioning processes and wherein the surface conditioning processesare varied to yield varying surface finishes between different portionsof a single layer or between different layers or portions of differentlayers.

BACKGROUND

A technique for forming three-dimensional structures (e.g. parts,components, devices, and the like) from a plurality of adhered layerswas invented by Adam L. Cohen and is known as ElectrochemicalFabrication. It is being commercially pursued by Microfabrica® Inc.(formerly MEMGenCorporation) of Van Nuys, Calif. under the name EFAB®.This technique was described in U.S. Pat. No. 6,027,630, issued on Feb.22, 2000. This electrochemical deposition technique allows the selectivedeposition of a material using a unique masking technique that involvesthe use of a mask that includes patterned conformable material on asupport structure that is independent of the substrate onto whichplating will occur. When desiring to perform an electrodeposition usingthe mask, the conformable portion of the mask is brought into contactwith a substrate while in the presence of a plating solution such thatthe contact of the conformable portion of the mask to the substrateinhibits deposition at selected locations. For convenience, these masksmight be generically called conformable contact masks; the maskingtechnique may be generically called a conformable contact mask platingprocess. More specifically, in the terminology of Microfabrica Inc. suchmasks have come to be known as INSTANT MASKS™ and the process known asINSTANT MASKING™ or INSTANT MASK™ plating. Selective depositions usingconformable contact mask plating may be used to form single layers ofmaterial or may be used to form multi-layer structures. The teachings ofthe '630 patent are hereby incorporated herein by reference as if setforth in full herein. Since the filing of the patent application thatled to the above noted patent, various papers about conformable contactmask plating (i.e. INSTANT MASKING) and electrochemical fabrication havebeen published:

-   -   1. A. Cohen, G. Zhang, F. Tseng, F. Mansfeld, U. Frodis and P.        Will, “EFAB: Batch production of functional, fully-dense metal        parts with micro-scale features”, Proc. 9th Solid Freeform        Fabrication, The University of Texas at Austin, p161, August        1998.    -   2. A. Cohen, G. Zhang, F. Tseng, F. Mansfeld, U. Frodis and P.        Will, “EFAB: Rapid, Low-Cost Desktop Micromachining of High        Aspect Ratio True 3-D MEMS”, Proc. 12th IEEE Micro Electro        Mechanical Systems Workshop, IEEE, p244, January 1999.    -   3. A. Cohen, “3-D Micromachining by Electrochemical        Fabrication”, Micromachine Devices, March 1999.    -   4. G. Zhang, A. Cohen, U. Frodis, F. Tseng, F. Mansfeld, and P.        Will, “EFAB: Rapid Desktop Manufacturing of True 3-D        Microstructures”, Proc. 2nd International Conference on        Integrated Micronanotechnology for Space Applications, The        Aerospace Co., April 1999.    -   5. F. Tseng, U. Frodis, G. Zhang, A. Cohen, F. Mansfeld, and P.        Will, “EFAB: High Aspect Ratio, Arbitrary 3-D Metal        Microstructures using a Low-Cost Automated Batch Process”, 3rd        International Workshop on High Aspect Ratio MicroStructure        Technology (HARMST'99), June 1999.    -   6. A. Cohen, U. Frodis, F. Tseng, G. Zhang, F. Mansfeld, and P.        Will, “EFAB: Low-Cost, Automated Electrochemical Batch        Fabrication of Arbitrary 3-D Microstructures”, Micromachining        and Microfabrication Process Technology, SPIE 1999 Symposium on        Micromachining and Microfabrication, September 1999.    -   7. F. Tseng, G. Zhang, U. Frodis, A. Cohen, F. Mansfeld, and P.        Will, “EFAB: High Aspect Ratio, Arbitrary 3-D Metal        Microstructures using a Low-Cost Automated Batch Process”, MEMS        Symposium, ASME 1999 International Mechanical Engineering        Congress and Exposition, November, 1999.    -   8. A. Cohen, “Electrochemical Fabrication (EFAB™)”, Chapter 19        of The MEMS Handbook, edited by Mohamed Gad-EI-Hak, CRC Press,        2002.    -   9. “Microfabrication - Rapid Prototyping's Killer Application”,        pages 1-5 of the Rapid Prototyping Report, CAD/CAM Publishing,        Inc., June 1999.

The disclosures of these nine publications are hereby incorporatedherein by reference as if set forth in full herein.

The electrochemical deposition process may be carried out in a number ofdifferent ways as set forth in the above patent and publications. In oneform, this process involves the execution of three separate operationsduring the formation of each layer of the structure that is to beformed:

-   -   1. Selectively depositing at least one material by        electrodeposition upon one or more desired regions of a        substrate.    -   2. Then, blanket depositing at least one additional material by        electrodeposition so that the additional deposit covers both the        regions that were previously selectively deposited onto, and the        regions of the substrate that did not receive any previously        applied selective depositions.    -   3. Finally, planarizing the materials deposited during the first        and second operations to produce a smoothed surface of a first        layer of desired thickness having at least one region containing        the at least one material and at least one region containing at        least the one additional material.

After formation of the first layer, one or more additional layers may beformed adjacent to the immediately preceding layer and adhered to thesmoothed surface of that preceding layer. These additional layers areformed by repeating the first through third operations one or more timeswherein the formation of each subsequent layer treats the previouslyformed layers and the initial substrate as a new and thickeningsubstrate.

Once the formation of all layers has been completed, at least a portionof at least one of the materials deposited is generally removed by anetching process to expose or release the three-dimensional structurethat was intended to be formed.

The preferred method of performing the selective electrodepositioninvolved in the first operation is by conformable contact mask plating.In this type of plating, one or more conformable contact (CC) masks arefirst formed. The CC masks include a support structure onto which apatterned conformable dielectric material is adhered or formed. Theconformable material for each mask is shaped in accordance with aparticular cross-section of material to be plated. At least one CC maskis needed for each unique cross-sectional pattern that is to be plated.

The support for a CC mask is typically a plate-like structure formed ofa metal that is to be selectively electroplated and from which materialto be plated will be dissolved. In this typical approach, the supportwill act as an anode in an electroplating process. In an alternativeapproach, the support may instead be a porous or otherwise perforatedmaterial through which deposition material will pass during anelectroplating operation on its way from a distal anode to a depositionsurface. In either approach, it is possible for CC masks to share acommon support, i.e. the patterns of conformable dielectric material forplating multiple layers of material may be located in different areas ofa single support structure. When a single support structure containsmultiple plating patterns, the entire structure is referred to as the CCmask while the individual plating masks may be referred to as“submasks”. In the present application such a distinction will be madeonly when relevant to a specific point being made.

In preparation for performing the selective deposition of the firstoperation, the conformable portion of the CC mask is placed inregistration with and pressed against a selected portion of thesubstrate (or onto a previously formed layer or onto a previouslydeposited portion of a layer) on which deposition is to occur. Thepressing together of the CC mask and substrate occur in such a way thatall openings, in the conformable portions of the CC mask contain platingsolution. The conformable material of the CC mask that contacts thesubstrate acts as a barrier to electrodeposition while the openings inthe CC mask that are filled with electroplating solution act as pathwaysfor transferring material from an anode (e.g. the CC mask support) tothe non-contacted portions of the substrate (which act as a cathodeduring the plating operation) when an appropriate potential and/orcurrent are supplied.

An example of a CC mask and CC mask plating are shown in FIGS. 1A-1C.FIG. 1A shows a side view of a CC mask 8 consisting of a conformable ordeformable (e.g. elastomeric) insulator 10 patterned on an anode 12. Theanode has two functions. One is as a supporting material for thepatterned insulator 10 to maintain its integrity and alignment since thepattern may be topologically complex (e.g., involving isolated “islands”of insulator material). The other function is as an anode for theelectroplating operation. FIG. 1A also depicts a substrate 6 separatedfrom mask 8. CC mask plating selectively deposits material 22 onto asubstrate 6 by simply pressing the insulator against the substrate thenelectrodepositing material through apertures 26 a and 26 b in theinsulator as shown in FIG. 1B. After deposition, the CC mask isseparated, preferably non-destructively, from the substrate 6 as shownin FIG. 1C. The CC mask plating process is distinct from a“through-mask” plating process in that in a through-mask plating processthe separation of the masking material from the substrate would occurdestructively. As with through-mask plating, CC mask plating depositsmaterial selectively and simultaneously over the entire layer. Theplated region may consist of one or more isolated plating regions wherethese isolated plating regions may belong to a single structure that isbeing formed or may belong to multiple structures that are being formedsimultaneously. In CC mask plating, as individual masks are notintentionally destroyed in the removal process, they may be usable inmultiple plating operations.

Another example of a CC mask and CC mask plating is shown in FIGS.1D-1G. FIG. 1D shows an anode 12′ separated from a mask 8′ thatcomprises a patterned conformable material 10′ and a support structure20. FIG. 1D also depicts substrate 6 separated from the mask 8′. FIG. 1Eillustrates the mask 8′ being brought into contact with the substrate 6.FIG. 1F illustrates the deposit 22′ that results from conducting acurrent from the anode 12′ to the substrate 6. FIG. 1G illustrates thedeposit 22′ on substrate 6 after separation from mask 8′. In thisexample, an appropriate electrolyte is located between the substrate 6and the anode 12′ and a current of ions coming from one or both of thesolution and the anode are conducted through the opening in the mask tothe substrate where material is deposited. This type of mask may bereferred to as an anodeless INSTANT MASK™ (AIM) or as an anodelessconformable contact (ACC) mask.

Unlike through-mask plating, CC mask plating allows CC masks to beformed completely separate from the fabrication of the substrate onwhich plating is to occur (e.g. separate from a three-dimensional (3D)structure that is being formed). CC masks may be formed in a variety ofways, for example, a photolithographic process may be used. All maskscan be generated simultaneously prior to structure fabrication ratherthan during it. This separation makes possible a simple, low-cost,automated, self-contained, and internally-clean “desktop factory” thatcan be installed almost anywhere to fabricate 3D structures, leaving anyrequired clean room processes, such as photolithography to be performedby service bureaus or the like.

An example of the electrochemical fabrication process discussed above isillustrated in FIGS. 2A-2F. These figures show that the process involvesdeposition of a first material 2 which is a sacrificial material and asecond material 4 which is a structural material. The CC mask 8, in thisexample, includes a patterned conformable material (e.g. an elastomericdielectric material) 10 and a support 12 which is made from depositionmaterial 2. The conformal portion of the CC mask is pressed againstsubstrate 6 with a plating solution 14 located within the openings 16 inthe conformable material 10. An electric current, from power supply 18,is then passed through the plating solution 14 via (a) support 12 whichdoubles as an anode and (b) substrate 6 which doubles as a cathode. FIG.2A, illustrates that the passing of current causes material 2 within theplating solution and material 2 from the anode 12 to be selectivelytransferred to and plated on the substrate 6. After electroplating thefirst deposition material 2 onto the substrate 6 using CC mask 8, the CCmask 8 is removed as shown in FIG. 2B. FIG. 2C depicts the seconddeposition material 4 as having been blanket-deposited (i.e.non-selectively deposited) over the previously deposited firstdeposition material 2 as well as over the other portions of thesubstrate 6. The blanket deposition occurs by electroplating from ananode (not shown), composed of the second material, through anappropriate plating solution (not shown), and to the cathode/substrate6. The entire two-material layer is then planarized to achieve precisethickness and flatness as shown in FIG. 2D. After repetition of thisprocess for all layers, the multi-layer structure 20 formed of thesecond material 4 (i.e. structural material) is embedded in firstmaterial 2 (i.e. sacrificial material) as shown in FIG. 2E. The embeddedstructure is etched to yield the desired device, i.e. structure 20, asshown in FIG. 2F.

Various components of an exemplary manual electrochemical fabricationsystem 32 are shown in FIGS. 3A-3C. The system 32 consists of severalsubsystems 34, 36, 38, and 40. The substrate holding subsystem 34 isdepicted in the upper portions of each of FIGS. 3A to 3C and includesseveral components: (1) a carrier 48, (2) a metal substrate 6 onto whichthe layers are deposited, and (3) a linear slide 42 capable of movingthe substrate 6 up and down relative to the carrier 48 in response todrive force from actuator 44. Subsystem 34 also includes an indicator 46for measuring differences in vertical position of the substrate whichmay be used in setting or determining layer thicknesses and/ordeposition thicknesses. The subsystem 34 further includes feet 68 forcarrier 48 which can be precisely mounted on subsystem 36.

The CC mask subsystem 36 shown in the lower portion of FIG. 3A includesseveral components: (1) a CC mask 8 that is actually made up of a numberof CC masks (i.e. submasks) that share a common support/anode 12, (2)precision X-stage 54, (3) precision Y-stage 56, (4) frame 72 on whichthe feet 68 of subsystem 34 can mount, and (5) a tank 58 for containingthe electrolyte 16. Subsystems 34 and 36 also include appropriateelectrical connections (not shown) for connecting to an appropriatepower source (not shown) for driving the CC masking process.

The blanket deposition subsystem 38 is shown in the lower portion ofFIG. 3B and includes several components: (1) an anode 62, (2) anelectrolyte tank 64 for holding plating solution 66, and (3) frame 74 onwhich feet 68 of subsystem 34 may sit. Subsystem 38 also includesappropriate electrical connections (not shown) for connecting the anodeto an appropriate power supply (not shown) for driving the blanketdeposition process.

The planarization subsystem 40 is shown in the lower portion of FIG. 3Cand includes a lapping plate 52 and associated motion and controlsystems (not shown) for planarizing the depositions.

In addition to teaching the use of CC masks for electrodepositionpurposes, the '630 patent also teaches that the CC masks may be placedagainst a substrate with the polarity of the voltage reversed andmaterial may thereby be selectively removed from the substrate. Itindicates that such removal processes can be used to selectively etch,engrave, and polish a substrate, e.g., a plaque.

The '630 patent provides various examples of useful planarizationmethods. These examples include mechanical (e.g., diamond lapping andsilicon carbide lapping), chemical-mechanical, and non-mechanical (e.g.,electrical discharge machining) planarization processes.

Further teachings of the '630 patent indicate that diamond lapping canbe performed using a single grade of diamond abrasive, e.g., about 1-6micron, or diamond abrasives of various grades. Lapping with differentgrades of abrasive can be performed using separate lapping plates, or indifferent regions of a single plate. For example, a coarse diamondabrasive can be applied to the outer region of a spinning circularlapping plate, and a fine diamond abrasive can be applied to the innerregion. A removable circular wall can be provided between the inner andouter regions to increase segregation. The layer to be planarized firstcontacts the outer region of the plate, then is optionally rinsed toremove coarse abrasive, and then is moved to the inner region of theplate. The planarized surface can then be rinsed using a solution, e.g.,water-based or electrolyte-based solution, to remove both abrasive andabraded particles from the planarized layer. The abrasive slurrypreferably is easily removable, e.g., water-soluble. Layer thickness,planarity and smoothness can be monitored, e.g., using an opticalencoder, wear resistant stops, and by mating the layer under a knownpressure with a precision flat metal plate and measuring the resistanceacross the plate-layer junction.

The '630 patent further provides an examples of a preferredplanarization processes. One includes allowing the work piece, i.e., thesubstrate having the layer to be planarized, to rotate within a“conditioning ring” on the lapping plate. Another involves lapping beingperformed by moving a workpiece around the surface of a lapping plateusing the X/Y motion stages of an electroplating apparatus withoutrotating or releasing the workpiece.

A need remains for improved electrochemical fabrication methods andapparatus that provide needed surface quality while optimizingproduction time. A need also remains for improved electrochemicalfabrication methods and apparatus that provide different surface qualityfor different regions of a structure that is being formed.

SUMMARY OF THE INVENTION

It is an object of certain aspects of the invention to provide animproved electrochemical fabrication process or apparatus that providesneeded surface quality without wasting production time.

It is an object of certain aspects of the invention to provide animproved electrochemical fabrication process or apparatus that providesdifferent surface qualities for different regions of a structure.

Other objects and advantages of various aspects of the invention will beapparent to those of skill in the art upon review of the teachingsherein. The various aspects of the invention, set forth explicitlyherein or otherwise ascertained from the teachings herein, may addressany one of the above objects alone or in combination, or alternativelymay not address any of the objects set forth above but instead addresssome other object ascertained from the teachings herein. It is notintended that all of these objects be addressed by any single aspect ofthe invention even though that may be the case with regard to someaspects.

In a first aspect of the invention an electrochemical fabricationprocess for producing a three-dimensional structure from a plurality ofadhered layers, includes (A) supplying a plurality of preformed masks,wherein each mask includes a patterned conformable dielectric materialthat includes at least one opening through which deposition can takeplace during the formation of at least a portion of a layer, and whereineach mask includes a support structure that supports the patternedconformable dielectric material; (B) selectively depositing at least aportion of a layer onto the substrate, wherein the substrate may includepreviously deposited material; (C) forming a plurality of layers suchthat each successive layer is formed adjacent to and adhered to apreviously deposited layer, wherein said forming includes repeatingoperation (B) a plurality of times; wherein at least a plurality of theselective depositing operations include(1) contacting the substrate andthe conformable material of a selected preformed mask; (2) in presenceof a plating solution, conducting an electric current through the atleast one opening in the selected mask between an anode and thesubstrate, wherein the anode includes a selected deposition material,and wherein the substrate functions as a cathode, such that the selecteddeposition material is deposited onto the substrate to form at least aportion of a layer; and (3) separating the selected preformed mask fromthe substrate; and (D) removing material deposited on at least one layerusing a first removal process that includes one or more operationshaving one or more parameters; and (E) removing material deposited on atleast one different layer using a second removal process that includesone or more operations having one or more parameters, wherein the firstremoval process differs from the second removal process by inclusion ofat least one different operation or at least one different parameter.

In a second aspect of the invention an electrochemical fabricationapparatus for producing a three-dimensional structure from a pluralityof adhered layers, includes (A) a plurality of preformed masks, whereineach mask includes a patterned conformable dielectric material thatincludes at least one opening through which deposition can take placeduring the formation of at least a portion of a layer, and wherein eachmask includes a support structure that supports the patternedconformable dielectric material; (B) means for selectively depositing atleast a portion of a layer onto the substrate, wherein the substrate mayinclude previously deposited material; (C) means for forming a pluralityof layers such that each successive layer is formed adjacent to andadhered to a previously deposited layer, wherein said forming includesrepeating operation (B)a plurality of times; wherein the means forselectively depositing includes (1)means for contacting the substrateand the conformable material of a selected preformed mask; (2) means forconducting, in presence of a plating solution, an electric currentthrough the at least one opening in the selected mask between an anodeand the substrate, wherein the anode includes a selected depositionmaterial, and wherein the substrate functions as a cathode, such thatthe selected deposition material is deposited onto the substrate to format least a portion of a layer; and (3) means for separating the selectedpreformed mask from the substrate; and (D) means for removing materialdeposited on at least one layer using a first removal process thatincludes one or more operations having one or more parameters; and (E)means for removing material deposited on at least one different layerusing a second removal process that includes one or more operationshaving one or more parameters, wherein the first removal process differsfrom the second removal process by inclusion of at least one differentoperation or at least one different parameter.

In a third aspect of the invention an electrochemical fabricationprocess for producing a three-dimensional structure from a plurality ofadhered layers includes (A) selectively depositing at least a portion ofa layer onto a substrate, wherein the substrate may include previouslydeposited material; (B) forming a plurality of layers such that eachsuccessive layer is formed adjacent to and adhered to a previouslydeposited layer; (C) removing material deposited on at least one layerusing a first removal process that includes one or more operationshaving one or more parameters; and (E) removing material deposited on atleast one different layer using a second removal process that includesone or more operations having one or more parameters, wherein the firstremoval process differs from the second removal process by inclusion ofat least one different operation or at least one different parameter.

In a fourth aspect of the invention an electrochemical fabricationprocess for producing a three-dimensional structure from a plurality ofadhered layers, the process including: (A) forming at least a portion ofa layer by either selectively depositing a material, to form portion ofa layer, onto a substrate or by selectively etching into a previouslydeposited material that occupies at least a portion of a layer and thendepositing a material into an opening formed by the selective etching,wherein the substrate may include previously deposited layers ofmaterial; (B) forming a plurality of layers such that subsequent layersare formed adjacent to and adhered to previously deposited layers; (C)finishing a surface of at least a portion of one or more materialsdeposited on at least one layer using a first process that includes oneor more operations having one or more parameters; and (E) finishing asurface of at least a portion of one or more materials deposited on theat least one layer using a second process that includes one or moreoperations having one or more parameters, wherein the portions subjectto the first and second processes are not identical and wherein thefirst process differs from the second process by inclusion of at leastone different operation, removal of at least one operation, or use of atleast one different parameter value.

In a fifth aspect of the invention an electrochemical fabricationprocess for producing a three-dimensional structure from a plurality ofadhered layers, the process including: (A) forming at least a portion ofa layer by either selectively depositing a material, to form portion ofa layer, onto a substrate or by selectively etching into a previouslydeposited material that occupies at least a portion of a layer and thendepositing a material into an opening formed by the selective etching,wherein the substrate may include previously deposited layers ofmaterial; (B) forming a plurality of layers such that subsequent layersare formed adjacent to and adhered to previously deposited layers; (C)finishing a surface of at least a portion of one or more materialsdeposited on at least one layer using a first process that includes oneor more operations having one or more parameters; and (E) finishing asurface of at least a portion of one or more materials deposited on atleast one different layer using a second process that includes one ormore operations having one or more parameters, wherein the first processdiffers from the second process by inclusion of at least one differentoperation, removal of at least one operation, or use of at least onedifferent parameter value.

Other aspects of the invention will be understood by those of skill inthe art upon reviewing the teachings herein. Other aspects of theinvention may involve apparatus that can be used in implementing one ormore of the above method aspects of the invention. These other aspectsof the invention may involve various combinations of the aspectspresented above, addition of various features of one or moreembodiments, as well as other configurations, structures, functionalrelationships, and processes that have not been specifically set forthabove.

In some embodiments, electrochemical fabrication processes produce oneor more three-dimensional structures (e.g. components or devices) from aplurality of layers of deposited materials wherein the formation of atleast some portions of some layers are produced by operations thatremove material, redistribute, condition, or otherwise finish selectedsurfaces of a deposited material. In some embodiments, removal,redistribution, conditioning, or finishing operations are varied betweenlayers or between different portions of a layer such that differentsurface qualities are obtained. In other embodiments varying surfacequality may be obtained without varying selected removal, redistributionor finishing operations or parameters but instead by relying ondifferential interaction between removal or conditioning operations anddifferent materials encountered by these operations.

In some embodiments a finishing process (e.g. removal or conditioningprocess) on a 1st layer differs from a removal or conditioning processon a 2nd layer. In some more focused embodiments the finishing processused on a 1st layer includes an operation not used in the finishingprocess used on a 2nd layer. In some other more focused embodiments, thefinishing process on a 2nd layer includes an operation not used in thefinishing process on the 1st layer. In some other embodiments thefinishing process on the 1st layer includes a parameter which isdifferent from a parameter used in the finishing process on the 2ndlayer.

In some embodiments a finishing process (e.g. removal or conditioningprocess) used on a 1st portion of a layer differs from the finishingprocess used on a 2nd portion of the layer. In some more focusedembodiments, the finishing process used on the 1st portion includes anoperation not used in the finishing process used on the 2nd portion. Insome more focused embodiments, the finishing process used on the 2ndportion includes an operation not used in the finishing process used onthe 1st portion. In some other embodiments, the finishing process usedon the 1st portion includes a parameter which is different from aparameter used in the finishing process used on the 2nd portion.

In some embodiments a selected finishing process (e.g. removal orconditioning process) is used on only a portion of a layer. In some morefocused embodiments the process is limited to operating on one or moreselected materials. In some more focused embodiments the process islimited to operating on one or more selected portions of one or moreselected materials. In some other more focused embodiments, the processis limited so as not to operate on one or more selected portions of oneor more selected materials. In some additional embodiments a mask havinga pattern of openings corresponding to a pattern of a selected materialforming a portion of the layer is used to define a surface on which theprocess will operate. In some further embodiments a mask having apattern of openings corresponding to non-outward facing surfaces of aselected material forming a portion of the layer is used to define thesurface on which the process will operate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C schematically depict side views of various stages of a CCmask plating process, while FIGS. 1D-1G schematically depict side viewsof various stages of a CC mask plating process using a different type ofCC mask.

FIGS. 2A-2F schematically depict side views of various stages of anelectrochemical fabrication process as applied to the formation of aparticular structure where a sacrificial material is selectivelydeposited while a structural material is blanket deposited.

FIGS. 3A-3C schematically depict side views of various examplesubassemblies that may be used in manually implementing theelectrochemical fabrication method depicted in FIGS. 2A-2F.

FIGS. 4A-4F schematically depict the formation of a first layer of astructure using adhered mask plating where the blanket deposition of asecond material overlays both the openings between deposition locationsof a first material and the first material itself

FIG. 4G depicts the completion of formation of the first layer resultingfrom planarizing the deposited materials to a desired level.

FIG. 5 depicts a flowchart of the generalized process of someembodiments of the instant invention.

FIG. 6A and 6B depict a CAD design of a scanning micro-mirror and anelectrochemically fabricated structure according to that design,respectively.

FIGS. 7A-7H set forth a side view (FIG. 7A) of a six layer structure aswell as top views (FIGS. 7B-7H) of the substrate and of each layer ofthat structure.

FIGS. 8A-8H illustrate a side view (FIG. 8A) and top views (FIGS. 8B-8H)of the structure of FIGS. 7A-7H where each of four distinct regions foreach layer are illustrated.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS. 1A-1G, 2A-2F, and 3A-3C illustrate various features of one form ofelectrochemical fabrication. Other electrochemical fabricationtechniques are set forth in the '630 patent referenced above, in thevarious previously incorporated publications, in various other patentsand patent applications incorporated herein by reference. Still othersmay be derived from combinations of various approaches described inthese publications, patents, and applications, or are otherwise known orascertainable by those of skill in the art from the teachings set forthherein. All of these techniques may be combined with those of thevarious embodiments of the invention to yield enhanced embodiments.Still other embodiments may be derived from combinations of the variousembodiments explicitly set forth herein.

FIGS. 4A-4F illustrate various stages in the formation of a single layerof a multi-layer fabrication process where a second metal is depositedon a first metal as well as in openings in the first metal so that thefirst and second metal form part of the layer. In FIG. 4A a side view ofa substrate 82 is shown onto which patternable photoresist 84 is cast asshown in FIG. 4B. In FIG. 4C a pattern of resist is shown that resultsfrom the curing, exposing, and developing of the resist. The patterningof the photoresist 84 results in openings or apertures 92(a)-92(c)extending from a surface 86 of the photoresist through the thickness ofthe photoresist to surface 88 of the substrate 82. In FIG. 4D a metal 94(e.g. nickel) is shown as having been electroplated into the openings92(a)-92(c). In FIG. 4E the photoresist has been removed (i.e.chemically stripped) from the substrate to expose regions of thesubstrate 82 which are not covered with the first metal 94. In FIG. 4F asecond metal 96 (e.g. silver) is shown as having been blanketelectroplated over the entire exposed portions of the substrate 82(which is conductive) and over the first metal 94 (which is alsoconductive). FIG. 4G depicts the completed first layer of the structurewhich has resulted from the planarization of the first and second metalsdown to a height that exposes the first metal and sets a thickness forthe first layer.

In some preferred embodiments of the invention electrochemicalfabrication processes or apparatus are provided that include enhancedremoval or finishing processes and apparatus. In particular the enhancedremoval or finishing processes involve use of one or more differentremoval of finishing operations and/or one or more different removal orfinishing parameters on at least two different layers. The use of oneprocess may allow faster, or otherwise preferred, removal or finishingoperations to occur for selected layers (e.g. when surface quality isnot critical) while a slower process may be used, or an otherwise lesspreferred removal or finishing process, when surface quality is morecritical. Thus, the use of different definable removal processes allowsprocess optimization to occur.

In other embodiments different finishing operations may be used ondifferent parts of a single layer or on different layers simply toobtain a desired difference in surface finish regardless of the overallprocessing time.

A flow chart depicting the general electrochemical fabrication processfor some embodiments of the invention is depicted in FIG. 5. Element 102depicts the beginning of the process while element 104 sets the layernumber variable “i”, to a value of one. Decision block 106 inquires asto whether or not the layer number variable “i” has exceeded the totalnumber of layers “N” for the structure being formed. If so, the processproceeds to and ends at element 108. Assuming the variable “i” has notexceeded the total number of layers “N”, the process proceeds to element112 which sets the deposition number variable “j” for layer “i” to avalue of one. Next, element 114 calls for the deposition of the materialassociated with deposition number “j” for layer “i”. Next, element 116increments the deposition number by one. After which, element 118inquires as to whether or not the deposition number exceeds the maximumnumber of depositions “M” associated with layer “i”. If not, the processloops back to element 114 and the next deposition for layer “i” isperformed. If “yes”, the process moves forward to element 122 where thefinishing process (e.g. removal, redistribution, or conditioningprocess) operation variable “k” is set to a value of 1. Next the processmoves to element 124 where the finishing process “k” is performed forlayer “i”. The finishing process “k” associated with any given layer “i”may or may not exist. If it exists it may involve an identical operationor parameters that were used on other layers, it may involve a differentoperation from that used on one or more layers, or it may involve asimilar operation used on other layers but with different associatedparameters. After performance of removal process “k” for layer “i”, theprocess proceeds to element 126 where an inquiry is made as to whetheror not the value of “k” equals the maximum number of finishingoperations “P” associated with layer “i”. If it does not, “k” isincremented by one (element 128) and the process loops back to element124 for performing the next removal operation for layer “i”. If “k” doesequal “P”, the layer value “i” is incremented by 1 as indicated byelement 132 and the process loops back to element 106. The value of “N”,the value of “M” for each layer “i”, the value of “P” for each layer“i”, the deposition processes associated with variable “j” for eachlayer “i”, and the finishing processes (i.e. operations and parameters)associated with variable “k” for each layer “i” can be held in the mindof an operator when a manual fabrication process is being used or theymay be set in a look up table, determined or specified via acalculation, or otherwise determined and specified for use by anautomated apparatus.

In some preferred embodiments of the present invention either the valueof variable “k” is different between at least two layers and/or theoperations or parameters associated with a given value of “k” for atleast two different layers are different.

For example, on one layer where surface finish is not critical, a singlerelatively course abrasive may be used in a single lapping process toremove material and planarize the layer whereas on a different layer twoor more lapping processes may be used where progressively finerabrasives may be used to yield a smoother surface than would be obtainedin the single removal operation. In an alternative process, a singlelapping operation may be used on two different layers but one of thelayers may additionally involve a buffing process or a polishing processsuch as CMP. In a further alternative, lapping or CMP may be used on twodifferent layers but the parameters under which the operations operatemay be changed.

In certain embodiments it may be desirable to use a finer abrasive tobring the layer to a desired level and then use a courser abrasive for ashort period of time to roughen the surface without significantlychanging its effective surface level. More generally, in somecircumstances operations and parameters may be chosen so that certainlayers are provided with a higher degree of smoothness while in othercircumstances, operations and parameters are chosen to provide a coursesurface without significantly causing the level or height of thematerial to deviate from a desired level or height.

If a mirror like surface were desired for a given layer, more time orcost could be spent on the finishing operation (e.g. planarizationoperation and polishing operation) for that specific layer whileallowing all other layers to undergo a faster or otherwise moreacceptable process. The layer or layers that undergo a more rigorous,difficult, costly, or time consuming removal process may include thelast layer of the structure, an initial layer of the structure, or maybe limited to one or more intermediate layers.

If at least two different materials are being used in the depositionprocess, e.g. at least one sacrificial material and at least onestructural material, then surface quality may be imparted eitherdirectly or indirectly by the finishing process. If the desired surface(i.e. the surface that is to have the desired attributes) is one that isbeing operated on by the removal process (e.g. planarized), the removalprocess imparts the quality to the surface directly and if the surfaceis associated with layer “i” then these removal operations are performedon layer “i”. If on the other hand, the desired surface is not one thatis being planarized, then the quality of it is being imparted from thesurface on which it was formed or will be formed (e.g. from theplanarization provided to the previously formed layer). In this lattercase, if the surface for which the particular quality is being sought isassociated with layer “i” then it is layer “i−1” that must receive thespecialized removal process. In other words if a structure is beingformed by stacking layers one on top of the other, it is the up-facingsurfaces of each layer that undergo removal, it is the up-facingsurfaces that obtain their surface qualities directly form the removaloperations whereas the down-facing surfaces pick up their surfacequalities as a result of the surface quality that was achieved on thepreviously formed layer. If the layers are being added below previouslyformed layers then roles of the up-facing and down-facing surfaces arereversed.

In other embodiments, finishing may be performed at least in part usingetchants that may be substantially non-selective with respect to theirability to etch materials being used in the formation of the structureor they may offer a significant level of selectivity for enhancedetching of one material relative to another. In still other embodimentselectrochemical etching or polishing may be used during some or allfinishing operations. In still other embodiments, finishing operationsmay involve a combined use of one or more etchants, mechanicaloperations, grinding or polishing operations, application of electricalcurrents or potentials, and the like.

The CAD design of a scanning micro-mirror device that can benefit fromvarious embodiments of the invention is depicted in FIG. 6A while amirror formed from that CAD file using an electrochemical fabricationprocess is shown in the SEM of FIG. 6B. The quality of the formed mirrorand particularly the surface quality of the upper surface of thereflective portion 200 of the mirror may benefit from the enhancedfabrication techniques of various embodiments of the present invention.In these embodiments, the layer containing the upper surface of themirror may undergo polishing operations which are not performed on otherlayers of the structure which can produce a mirror of desiredreflectivity while not hindering the overall build process with such ahigh level of polishing on each layer.

In some embodiments, the selective application of specialized surfacefinishing may provide not only smoother surfaces when desired but alsorougher surfaces or surfaces with other qualities when appropriate. Forexample, in some applications adhesion between successive layers may beenhanced by roughening the surface prior to deposition of the structuralmaterial associated with the next layer. In still other embodiments,significantly roughing or otherwise treating the surface may decreaseundesirable spectral reflections from that surface. For example in FIG.6B, it may be desirable to roughen or otherwise treat surfaces 202, 204,206, 208, 210 and 212 to decrease such reflections. If one or more ofthese additional surfaces exist on the same layer where other finishingprocesses are desired (such as for surfaces 200, 204, 206, 208 and 210)it may be necessary to selectively perform two or more finishingprocesses independently of one another. Alternatively, it may bepossible to perform a first finishing process in a blanket manner withthe subsequent processes formed in selective manners where the result ofthe first finishing process is simply the starting point for thesubsequent operations. Of course, those of skill in the art willunderstand that other levels of processing selectivity or processingorder are possible. For example, if a first selectively appliedfinishing process creates a great disparity between surface finishes oftwo distinct regions then a common blanket finishing operation may beused which still leaves a desired level of disparity between relevantattributes of the distinct regions. As a further example, after aninitial planarization operation brings a given layer to a desired leveland to a desired surface finish, a thin blank deposition or selectivedeposition of a desired coating material may be made, after whichadditional selective or blanket finishing operations may be used to takethe entire surface or a portion of the surface to a final finishedstate.

In some embodiments it may be desirable to select, or tailor, thesurface finish associated with a given portion of a layer depending onhow that portion relates to the presence or lack of presence ofstructural material in the same area on a subsequent layer that is to beformed. In other embodiments, similar consideration of sacrificialmaterials may be used.

In some embodiments a single structural material will be used and thatstructural material will typically overlay at least in part, structuralmaterial deposited on a previous layer or structural material to bedeposited on a subsequent layer. In these embodiments, structuralmaterial on each portion of a layer may be classified into one of fourcategories: (1) up facing, (2) down facing, (3) both up facing and downfacing, or (4) continuing. An up facing portion of structural materialon a given layer is that portion of the structural material that is notbounded by structural material that is associated with the next higherlayer level. A down facing region of structural material on a givenlayer is that portion of the structural material that is not boundedfrom below by structural material located on the layer that is locatedimmediately below the given layer. A portion of structural materialdefined as both up facing and down facing is not bounded from above orbounded from below by structural material that exists on the next higherlayer or on the previous lower layer, respectively. Finally, a portionof structural material located on a given layer that is bounded frombelow and bounded from above by structural material on the immediatelysucceeding layer and preceding layer, respectively, is a continuingregion.

In other embodiments layers need not be stacked along a vertical axisand thus the above terms may either be defined for a different buildorientation or alternatively they may simply be reinterpreted in anappropriate way. In embodiments where more than one structural materialis used and/or more than one sacrificial material is used, additional oralternative distinct regions may be defined as necessary. In still otherembodiments where sensitivity to certain structural features iscritical, alternative or added regions may be defined. In still otherembodiments where boundary effects between distinct regions, or otherissues, make it desirable to define regions which are slightly larger orsmaller than what is ascertainable from layer to layer comparisonsalone, offset boundaries may be defined using erosion techniques orexpansion techniques

FIGS. 7A-7H set forth a side view of a six layer structure as well astop views of each layer of that structure. FIG. 7A depicts a side viewof a six layer structure that includes layer portions that are definablein each of the four distinct categories noted above. For simplicitysake, the structure is assumed to be formed by stacking layers on top ofone another starting with the first layer 301 formed on top of asubstrate 300 followed by layers 302 to 306. Each layer comprises aportion that is formed of structural material 314 and a portion formedfrom a sacrificial material 316. A top view of the substrate 300 isshown is FIG. 7B. The regions of structural material on layer 301 areshown in FIG. 7C relative to an outline 310 of the substrate. FIGS.7D-7H show structural material associated with layers 302 to 306,respectively, relative to an outline 310 of substrate 300.

FIGS. 8A-8H illustrate a side view and top views of the structure ofFIGS. 7A-7H where each of the four distinct regions for each layer areillustrated. FIG. 8A shows that a structure 308 is formed on a substrate300 from layers 301 to layers 306. FIG. 8A also indicates that differentportions of each layer can be classified into the different regionsdiscussed above (where like regions are designated with like fillpatterns). It can be seen that continuing regions 322 exist on somelayers, regions that are both up facing and down facing 324 exist onsome layers, regions that are down facing only 326 exist on some layers,and regions that are up facing only 328 exist on some layers. FIGS.8B-8H illustrate top views of the substrate and each of layers 301through 306, respectively, where distinct regions 322, 324, 326, and 328are shown with fill patterns similar to those illustrated in FIG. 8A.

The recognition of distinct portions (or regions) of layers may be usedin tailoring finishing processes that may be used in achieving desiredsurface finishes for each portion of each layer. In some alternativeembodiments, if desired, sacrificial material may also receive similardesignations which may be used for determining additional or alternativesurface finishing processes that may be used.

Once the distinct regions of each layer are determined, an associateddesired surface quality parameter may be associated with each region.From the combined surface quality parameters associated with each layerappropriate surface finishing or treatment processes may be proposed andan order for performance proposed. From an analysis of the proposedprocesses and order, conflicts may be determined and either removed byprocess or order modifications or alternatively by deciding to use fallback or compromise finishing processes.

In some embodiments where structures will be formed by stacking layersone above the other, it may be appropriate to associate portions of anext layer (n+1) that are down-facing with the previous layer (n) sothat appropriate finishing operations may be used on at least portionsof the sacrificial material so that those portions have appropriatesurface finish after forming the previous layer (n) which will be usedin setting the surface quality of the down-facing features of structuralmaterial on the next layer (n+1). In embodiments with other buildorientations (e.g. subsequent layers formed below previously formedlayers) other appropriate associations may be made.

As an example of how different surface finishes may be applied to asingle layer one may consider layer 304 of FIG. 8F. In this layer it maybe seen that a portion of the structural material is continuing 322 anda portion is up-facing 328 or 324. If it is desired that up facingsurfaces have a relatively smooth surface finish and that non-up-facingregions may have an alternative surface finish (e.g. one which is formedfaster or one which is intentionally roughened up to, for example,enhance adhesion between layers), the entire layer may be planarized orpolished to the extent desired to obtain the surface finish to beassociated with up-facing features (assuming any exist on the layerbeing considered) then a contact mask or other mask may be placedagainst the resulting surface. The solid portions of the mask may bepressed against the portion of the surface(s) that are to retain thedesired “up-facing” finish and the openings in the mask may be locatedover those portions of the surface(s) that are intended to have adifferent finish (e.g. rougher finish). The exposed surface(s) may betreated with an appropriate chemical etch, electrochemical etch,reactive or inactive material bombardment, radiation bombardment, or thelike which is intended to produce the desired surface finish. Afterappropriate selective treatment, the mask may be removed. The operationsto produce the surface finish may or may not significantly change thelevel of the exposed surface.

In other embodiments where a third distinct surface finish is desired afurther mask of selected configuration may be placed on or contacted tothe surface leaving openings in the regions to be treated. The selectivetreatment may be applied after which the mask may be removed. In stillother embodiments surface treatments that are performed may includedeposition operations or redistribution operations (e.g. alternateetchings and depositions) as opposed to, or in addition to, the removaloperations.

The method embodiments of the present invention may be implementedmanually or via an automated or semi-automated apparatus. The apparatusused for either manual or automated execution of the methods may involveappropriate deposition stations (e.g. one or more selective depositionstations and one or more blanket deposition stations), one or more layerfinishing or removal stations set up or modifiable to implement thespecific type of removal operations to be performed, capability tomonitor deposit height or level during removal operations or betweenremoval operations, one or more cleansing or activation stations, one ormore inspection stations. Various apparatus configurations are withinthe skill of the art based on the teachings herein. A number ofalternatives are disclosed in the previously referenced and incorporated'630 patent.

Preferred apparatus for implementing the present invention will involveone or more programmed computers that control the process flow andassociated operations and parameters.

Various other embodiments of the present invention exist. Some of theseembodiments may be based on a combination of the teachings herein withvarious teachings incorporated herein by reference. Some embodiments maynot use any blanket deposition process. Some embodiments may involve theselective deposition of a plurality of different materials on a singlelayer or on different layers. Some embodiments may use blanketdepositions processes that are not electrodeposition processes. Someembodiments may use selective deposition processes on some layers thatare not electrodeposition processes. Some embodiments may use nickel asa structural material while other embodiments may use differentmaterials such as gold, silver, or any other electrodepositablematerials that can be separated from a sacrificial material such ascopper. Some embodiments may use copper as the structural material withor without a sacrificial material. Some embodiments may remove asacrificial material while other embodiments may not. In someembodiments, the depth of deposition will be enhanced by pulling aconformable contact mask away from the substrate as deposition isoccurring in a manner that allows the seal between the conformableportion of the CC mask and the substrate to shift from the face of theconformal material to the inside edges of the conformable material. Insome embodiments, manual or automated visual inspection of a deposits orplanarized surfaces may occur.

In view of the teachings herein, many further embodiments, alternativesin design and uses of the instant invention will be apparent to those ofskill in the art. As such, it is not intended that the invention belimited to the particular illustrative embodiments, alternatives, anduses described above but instead that it be solely limited by the claimspresented hereafter.

1. An electrochemical fabrication process for producing athree-dimensional structure from a plurality of adhered layers, theprocess comprising: (A) supplying a plurality of preformed masks,wherein each mask comprises a patterned conformable dielectric materialthat includes at least one opening through which deposition can takeplace during the formation of at least a portion of a layer, and whereineach mask comprises a support structure that supports the patternedconformable dielectric material; (B) selectively depositing at least aportion of a layer onto the substrate, wherein the substrate maycomprise previously deposited material; (C) forming a plurality oflayers such that each successive layer is formed adjacent to and adheredto a previously deposited layer, wherein said forming comprisesrepeating operation (B) a plurality of times; wherein at least aplurality of the selective depositing operations comprise (1) contactingthe substrate and the conformable material of a selected preformed mask;(2) in presence of a plating solution, conducting an electric currentthrough the at least one opening in the selected mask between an anodeand the substrate, wherein the anode comprises a selected depositionmaterial, and wherein the substrate functions as a cathode, such thatthe selected deposition material is deposited onto the substrate to format least a portion of a layer; and (3) separating the selected preformedmask from the substrate; and (D) removing material deposited on at leastone layer using a first removal process that comprises one or moreoperations having one or more parameters; and (E) removing materialdeposited on at least one different layer using a second removal processthat comprises one or more operations having one or more parameters,wherein the first removal process differs from the second removalprocess by inclusion of at least one different operation or at least onedifferent parameter.
 2. The process of claim 1 wherein the first andsecond removal processes comprise lapping operations, and wherein one ofthe removal processes comprises a lapping operation that uses a finerabrasive than that used by the other removal process.
 3. The process ofclaim 1 wherein the first and second removal processes comprise lappingoperations, and wherein one of the removal processes comprises one ormore additional lapping operations than does the other removal process.4. The process of claim 1 wherein one of the first or second removalprocesses comprises a finer removal process than the other removalprocess.
 5. The process of claim 4 wherein the finer removal processresults in a surface with mirror-like optical properties.
 6. The processof claim 4 wherein the finer removal process is used after deposition ofmaterial for a final layer of the structure.
 7. The process of claim 4wherein the finer removal process is used after deposition of materialfor an intermediate layer of the structure.
 8. The process of claim 5wherein the mirror-like properties exist on a surface of the structurethat undergoes a removal process.
 9. The process of claim 5 wherein themirror-like properties exist on a surface of the structure that did notundergo a removal process but instead acquired the mirror-likeproperties as a result of deposition of material onto a mirror-likesurface.
 10. The process of claim 1 wherein the formation of a pluralityof layers includes the deposition of at least a second material.
 11. Theprocess of claim 10 wherein the second material is a structural materialand the selected deposition material is a sacrificial material
 12. Theprocess of claim 1 wherein at least one of the first and second removalprocesses comprises CMP.
 13. The process of claim 1 wherein at least oneof the first or second removal processes comprise multiple lappingoperations where at least two different abrasives are used.
 14. Theprocess of claim 13 wherein use of a rougher abrasive on a given layeris followed by use of a finer abrasive.
 15. The process of claim 13wherein use of a finer abrasive is followed by use of a rougher abrasive16. The process of claim 15 wherein finer abrasive is used for a longertime than the rougher abrasive.
 17. The process of claim 1 whereindepositions associated with at least one or more layers are subjected toa third removal process that is different from both the first and secondremoval processes.
 18. The process of claim 1 wherein the conformablematerial comprises an elastomeric material.
 19. The process of claim 11wherein at least one of the removal processes involves use of aselective etchant that attacks either the sacrificial material or thestructural material but not both.
 20. The process of claim 1 wherein atleast one of the removal processes involves use of an electropolishingprocess.